Make a mental note, im only doing the most common profitable skills that people do. Still under construction. *=members only skill.

Combat: This is a guide of generally what monsters will get you the most xp, for your level. Again, this is just some guesses at what YOU should kill at YOUR level.

Combat levels 3-8: regular old rats will do fine. These can be find in Lumbridge, near the castle, south of the entrance to the castle.
Combat levels: 11-20: level 3 and 6 Giant rats, behind Lumbridge Castle.
Combat levels: 21-30: level 9 Al Kharid Warriors, in the Al Kharid Palace.
Combat levels: 31-40: Level 18 skeletons, in Edgeville Dungeon, just North of the entrance in Edgeville.
Combat levels: 41-50: Level 21 guards, found guarding Falador and Varrock for non members, and Ardougne and many others for members.
Combat levels: 51-60: Level 28 Shantay Guards, at the Shantay Pass
Combat levels: 61-70: Level 32 Kalphites, in the Kalphite lair.
Combat levels: 71-80: Level 42 Moss Giants, found West of the fishing guild.
Combat levels: 81-90: level 53 Ogres, East of Castle Wars.
Combat levels: 92+: level 82 lesser demons, in the Karamja Volcano.


Fishing: This is what you should fish for the best xp.

1-39: Fish whatever you can catch at your level, it doesn't really matter.
40-76: Lobbies,Lobbies,Lobbies...Their such good xp.
76+: they may be slow at first, but they are awesome for earning cash, they're 1k ea! They're sharks! But Lobbies r still better xp....so....
76-85: Lobbies...
85+: Now u do sharks!!!
Prices: anything below fishing lvl of lobbies: just sell to the freaking general store nobody buys them...
Raw Lobbies: 200-250gp each.
Cooked Lobbies: 200-230gp each.
Raw Shark: 900-1000gp each.
Cooked shark: 1000-1100gp each.

Woodcutting:
1-15:what choice do you have! cut normal trees and make fires from the logs...No one will buy them anywway.
15-30:what choice do you have, cut oaks and make fires out of them, no one buys those either.
30-70: willows all the way! sell the willow logs for 25gp each, make sure you have at least 500 before trying to sell them.
70-99: Cut yews, in fact, i'm thinking you should go yews all the way to 99!
99: Cut mages, they wont be very slow because your 99, so their amazing $, so unless you want to go for 200,000,000 wc xp, cut mages, yews are still better xp though.


Mining/Smithing: you know what to do, mine what you can, smith what you can, SELL what you can!


Herblore*
Bottom line: AMAZING WAY TO EARN MONEY!!! you can sell antpoisons 1kgp each, and their lvl 5 to make! Prayer Pots prices are changing daily, but people will sometimes pay small fortunes just for one!